Apparatus and a method of inspecting pieces of cloth

ABSTRACT

The invention relates to a method and an apparatus for automatic inspection of flatly positioned pieces of cloth with a view to detecting impurities or other irregularities in pieces of cloth. The pieces of cloth are transported past a camera ( 10 ) that is, in cooperation with a digital storage unit, configured for producing a digital image of each piece of cloth or portions of each piece of cloth; and wherein the apparatus comprises one or more light emitters ( 11 ) with a view to illuminating at least that part of a piece of cloth that is within the field of vision of the camera ( 10 ). According to the invention each piece of cloth is conveyed from a receiver conveyor ( 12 ) to a delivery conveyor ( 13 ), the field of vision of the camera ( 10 ) being configured for comprising at least an open area ( 14 ) between these to conveyors ( 12, 13 ), whereby the digital image is recorded during the passage of a piece of cloth from the receiver conveyor ( 12 ) to the delivery conveyor ( 13 ).

[0001] The present invention relates to an apparatus as featured in thepreamble to claim 1 and a method as featured in the preamble to claim 8.

[0002] By such methods and apparatuses it was previously known to conveyeach piece of cloth on the top side of a conveyor past a camera that islocated above the conveyor and photographically records the piece ofcloth from above. In those cases where the piece of cloth has just lefta rotary ironer following preceding laundering, it is advantageous toinspect that side of the piece of cloth that had been facing the ironingside, since this is the most smooth side and hence the side on whichimpurities and irregularities will be most visible.

[0003] Such inspection from the ironing side has entailed that thepieces of cloth were to be turned before the inspection was carried out,which makes demands to both extra space and extra equipment. There issimultaneously a requirement, in special cases, for being able toinspect both sides of a piece of cloth, which also makes requirements toeach piece of cloth being turned.

[0004] It is the object of the invention to provide a method and anapparatus that will, without need for additional space or equipment,enable inspection of the side of the pieces of cloth that has beenfacing the ironing side of a rotary ironer, and which enable inspectionof both the one and the other or both sides of pieces of cloth.

[0005] This is obtained by an apparatus and a method as featured inclaim 1 and claim 8, respectively.

[0006] By allowing the pieces of cloth to pass an open area between twoconveyors, it becomes possible to inspect the piece of cloth from eitherthe one or the other side in the open area between the conveyors. Thusit is possible to inspect a piece of cloth from the side that facestowards the ironing side after the piece of cloth has left a rotaryironer, even in case it is the side that faces towards the receiverconveyor due to the fact that the inspection takes place in an open areabetween the receiver conveyor and the delivery conveyor. Thus, therecording of the digital images that is a prerequisite for theinspection to take place from the side(s) that is/are most appropriatein the relevant situation.

[0007] It will be possible herein to configure the receiver conveyor ata higher level than the delivery conveyor, whereby the passage from theone to the other conveyor is accomplished substantially vertically andsuch that the inspection is accomplished in accordance with asubstantially horizontal line of sight. However, this is associated withcertain difficulties during the passage of the end of the pieces ofcloth that will have a propensity to drop down onto the deliveryconveyor when an end portion of the piece of cloth reaches the end ofthe receiver conveyor.

[0008] It is therefore preferred that the delivery conveyor and thereceiver conveyor are located essentially flush with each other, theinspection being performed along a line of sight that is substantiallyperpendicular to the two preferably horizontally extending conveyors.

[0009] As stated in claim 2 there is between the camera and the areabetween the two conveyors located a transparent cover. Hereby a physicalbarrier is obtained that is able to separate the very sensitiveelectronics in the camera from the pieces of cloth. This is particularlyimportant in laundries where the pieces of cloth come from a rotaryironer and thus emit both heat and moisture that may adversely influencethe camera and the light emitters. Conveniently the covering isconfigured as a glass board.

[0010] The receiver conveyor and the delivery conveyor being locatedessentially in extension of each other and configured for conveying thepiece of cloth slidingly across the transparent cover between them, itis obtained that the transparent cover is continuously cleaned ofdeposits, if any, in the form of fluff or other impurities.

[0011] Advantageously the transparent cover forms a window in a closedcontainer, in which the camera is located. Hereby it is possible tomonitor accurately the climate in which the camera is situated such thatconstant temperature and humidity can be maintained. Thereby optimal andconstant conditions of operation for the camera are ensured. The widthof the pieces of cloth that are to be photographed by the camera beingconsiderable, a mirror arrangement is conventionally used that providesan optical distance between the camera and the pieces of cloth that isclose to the maximal width, and by positioning these mirrors in theclosed container, the mirrors are safeguarded against deposits ofparticles and fluff that might otherwise adversely affect the quality ofthe images recorded.

[0012] Advantageously, the light emitters are arranged between thecamera and the transparent cover, due to the fact that the transparentcover thereby also protects the light emitters. The light emitters canconveniently be arranged in the closed container. Of course it is alsopossible to arrange one or more light emitters opposite the transparentcover, and in that case the camera will record an image that derives atleast partially from light transmitted through the pieces of cloth.

[0013] Advantageously a light emitter is configured as an elongate lightguide arranged transversally to the two conveyors along the area locatedthere between, and such that the light guide is supplied with light atone or both ends, and wherein the light guide is configured for emittinglight along the longitudinal axis of the light guide.

[0014] Light emitters of this type are known, but herein the particularadvantage is obtained that the strongly heat-emitting light source canbe arranged at a suitable distance from the camera and in a place whereit is easy to provide for a suitable cooling. In previously knownapparatuses for this type of inspection, fluorescent tubes, such as egneon tubes were used, but it has been found to be difficult to obtain anentirely uniform illumination over the width that is required in case oflaundry machines, and besides the replacement of burnt-out neon tubeshave required more protracted operation halts with ensuing adverseeffects on the production. Finally it is necessary to locate thefluorescent tubes quite close to the pieces of cloth, which has resultedin a heating of the pipes with ensuring variations in the lightemission. Further it should be noted that light guides are considerablyless space-consuming than fluorescent tubes, which makes it possible tokeep the open space between the two conveyors suitably narrow, wherebythe distance to be travelled by the piece of cloth without beingsupported by a conveyor is limited as much as possible.

[0015] A convenient configuration of the light guides is obtained incase they each comprise a glass rod that has, along its longitudinalaxis, dispersion means for causing the light to leave the glass rodalong the longitudinal axis. A suitable dispersion means could in thiscase be constituted of one or more ground facets distributed along thelongitudinal axis of the rod. The ground surface(s) of a facet willdisperse the light and thus the dispersed light will hit the surface ofthe glass rod at an angle that allows the light to leave the rod.Conveniently rods of quartz glass are used that are transparent to alight over a wide wavelength area.

[0016] Use of light guides of the above-mentioned type makes itparticularly simple to insert filters at the end of each rod between therod and the light source. Thus, the spectral composition of the lightcan be regulated in accordance with the type of laundry to be inspected.Replacement of burnt-out bulbs in the light source can be carried out ina readily accessible spot at a side portion outside the closedcontainer, and thus replacement of bulbs becomes possible withoutconsiderable operational disturbances.

[0017] It is preferred to use light with a mixture of wavelengths in theultraviolet range and the blue-violet range.

[0018] Now follows a detailed explanation of an exemplary, concreteembodiment of the invention with reference to the figures of thedrawing, wherein

[0019]FIG. 1 shows a lateral view of a rollway, comprising a rotaryironer, an inspection apparatus according to the invention and a foldingmachine; and

[0020]FIG. 2 is an enlarged sectional view of FIG. 1 and shows theinspection apparatus in combination with the receiver conveyor.

[0021]FIG. 1 shows a common rotary ironer 1, to the outlet end of whichthere is coupled a receiver conveyor 12. The pieces of cloth areconveyed from the receiver conveyor 12 onto a delivery conveyor 13 andfrom there the pieces of cloth are delivered to eg a folding machine 2that folds the pieces of cloth. Between the receiver conveyor 12 and thedelivery conveyor 13 there is an open space 14, where the pieces ofcloth are not supported by a conveyor. Underneath the open area there islocated a camera 10 that is, via a number of mirrors S1, S2 and S3,configured for photographing the area 14 between the two conveyors.

[0022] In the example shown in FIG. 1 the receiver and deliveryconveyors follow each other at approximately the same level, but it isalso an option to configure the delivery conveyor 12 at a level belowthe receiver conveyor 13, whereby the pieces of cloth will, during thetransfer between the conveyors, be freely suspended, and then toconfigure the camera 10 with a substantially horizontal line of sight.Hereby the same advantage could be obtained, viz that the camera 10 canbe configured to watch any of the two sides of the piece of cloth.

[0023] As shown in FIG. 1 and in the current example, the camera 10 islocated underneath the open area between the conveyors 12, 13 and thusthe camera 10 will record and image of that side of the piece of cloththat has faced towards the ironing side of the rotary ironer 1. This isa considerable advantage over previous systems, since the ironing sideis the most smooth, and the side where discolourations, if any, thatwere not removed during the preceding laundering procedure are mostvisible.

[0024] In the area 14 between the two conveyors 12,13 there is arrangeda transparent cover plate 15 that serves several purposes. It supportsthe piece of cloth between the two conveyors, and in this context it hassurprisingly been found that it is possible, without any problemswhatsoever, to push the front end of a piece of cloth transversallyacross the cover plate 15 without folds occurring in the piece of cloth.The cover plate 15 also contributes to making a physical shield for thecamera 10. This is important, since—during passage of the apparatus—thepieces of cloth will emit both a certain amount of heat and some degreeof moisture, which may adversely influence the operational stability ofthe camera 10.

[0025] For the same reason the cover plate 15 forms a window in acontainer 16, in which the camera 10 is located along with theassociated mirror arrangement. Thereby it is possible to maintain aconstant climate around the camera 10. Simultaneously it is ensured thatfluff and other impurities, which are unavoidable in the surroundings ofa laundry, are not deposited on the mirrors.

[0026]FIG. 2 is an enlarged reproduction of the container 16 as suchwith the camera 10. The travelling of the light from the underside of apiece of cloth to the camera is also shown herein. The travelling of thelight from the underside of the glass plate 15 via the mirrors S1, S2,S3 and further on to the camera 10 is shown by lines L1, L2, L3 and L4.

[0027] The glass rods 11 are located in each their holder, and at theend of each rod, lights sources are provided that are not shown in thefigure. The light sources are commercially available sources that emitlight in a desired spectral area. In the embodiment shown in FIGS. 1 and2, the rods 11 are located to each side of the line L1, and therebysymmetrical illumination of the piece of cloth across the glass plate isobtained and the advantage of this is that folds, if any, generatedduring the ironing process do not entail shadow formation that could beinterpreted as impurities in the piece of cloth. If a sufficientlystrong light source is used, however, a rod will often be sufficient,which is financially advantageous.

[0028] This type of light emitters is associated with the problem thatthe light intensity has a propensity to decrease with increasingdistance from the light source, and that the light will have apropensity to leave the rod at a relatively acute angel relative to thelongitudinal axis of the rod. It has been attempted to solve theseproblems by grinding a number of discrete facets in the rod surface,whereby the ground surface of each facet will serve as diffusion face.Variations in the distance between the facets enable a more evenemission of light along the longitudinal axis of the rod, and selectionof the angle between the surface of the facets and the longitudinal axisof the rod serves to ensure that the light leaves the rod at an anglethat is rather close to 90°. By these measures it is possible to achieveuniform emission of light along the entire expanse of the rod and at anangle that does not presuppose a length of the rod that does notconsiderably exceed the width of the conveyors.

[0029] The area of the glass plate 15 and this of the piece of cloththat is to be illuminated need not have a width of more than about 2 mmfor the sake of the camera. To obtain a high light intensity, it may beadvantageous to position an optical lens between the glass rod 11 andthe plate 15. Hereby the light emitted from the rod can be focused in anarrower area and hence a higher light intensity is accomplished.Likewise, a focusing effect can be obtained by selecting glass rods thatdo not feature circular cross-sections as shown; they rather have across section that comprises two straight parallel sides and twocircular arches that connect each of the two sides. In this context thefacets are ground in the one circular arch and the light will then leaveby the opposite arch.

[0030] It is preferred to use a light source that emits light within thespectral range of from 350 nm to 500 nm. Albeit the lower portion ofthis interval is not visible to the camera, the addition of opticalwhitener to the laundry detergents will enable that the light receivedby the pieces of cloth within the lower spectral range will be reflectedwithin the visible area around 450 nm. Hereby a marked improvement isobtained of the contrast between clean and not clean portions of thepiece of cloth, due to the not-clean areas having a propensity to blockthe effect of the contents of optical whitener of the piece of cloth.

[0031] In the area above the glass plate 15, a cap 18 is provided thatprevents light conditions prevailing in the surrounding environment frominfluencing the illumination of the piece of cloth.

[0032] Advantageously the glass plate 15 can be located at a level thatis slightly above the level for the receiver and delivery conveyors inorder to thereby ensure that each piece of cloth is caused to slideagainst the glass plate. Thereby the glass plate is continuously keptclean which is an essential prerequisite for successful photographing ofthe piece of cloth.

[0033] A usual gangway 19 is provided in the area above one of theconveyors.

[0034] In a known manner the camera is configured for recording one lineat a time in the transverse orientation of the piece of cloth and bycollecting the lines, an overall image is obtained in a conventionalmanner of what passes by on the glass plate 15. In a conventionalcomputer this overall image is formed and analysed; in the firstinstance to separate the individual pieces of cloth from thesurroundings, and subsequently to subject the image of each piece ofcloth to an analysis to detect impurities, spots or defects in thefabric; and on the basis of the result a signal is emitted to thefolding machine 2 to which destination the piece of cloth in question isto be sorted to go to.

[0035] It will be possible within the framework of the system to alsoapply a bar code to each piece of cloth, which bar code is decoded bythe analysis of the image of the piece of cloth and that identifies eachpiece of cloth. Use of suitable wavelengths of the illumination willalso enable such configuration of a bar code that it is more or lessinvisible to the eye, but readily readable to the camera.

[0036] The two conveyors 12 and 13 can be independent units, or they canbe integral parts of the rotary ironer and the folder, respectively.

1. An apparatus for automatic inspection of flatly positioned pieces ofcloth with a view to detecting impurities or other irregularities;wherein the apparatus comprises means for transporting the pieces ofcloth past a camera (10) that is, in cooperation with a digital storageunit, configured for producing a digital image of each piece of cloth orportions of each piece of cloth; and wherein the apparatus comprises oneor more light emitters (11) with a view to illuminating at least thatpart of a piece of cloth that is within the field of vision of thecamera (10), characterised in that the conveyance means comprises areceiver conveyor (12) and a delivery conveyor (13), the field of visionof the camera (10) being configured for comprising at least an open area(14) between these to conveyors (12, 13), whereby the digital image isrecorded during the passage of a piece of cloth from the receiverconveyor (12) to the delivery conveyor (13).
 2. An apparatus accordingto claim 1, characterised in that—between the camera (10) and the area(14) between the two conveyors (12, 13) a transparent cover (15) isarranged.
 3. An apparatus according to claim 2, characterised in thatthe receiver conveyor (12) and the delivery conveyor (13) followessentially in extension of each other and are configured for conveyingthe piece of cloth slidingly across the transparent cover (15).
 4. Anapparatus according to claim 2, characterised in that the transparentcover (15) forms a window in a closed container (16) in which the camera(10) is located.
 5. An apparatus according to claim 4, characterised inthat the light emitters (11) are arranged between the camera (10) andthe transparent cover (15).
 6. An apparatus according to claims 14,characterised in that the apparatus has at least one light emitter (11)that is configured as an elongate light guide arranged transversally tothe two conveyors (12, 13) along the area (14); and wherein the lightguide (11) is supplied with light at one or both ends and is configuredfor emitting light along its longitudinal axis.
 7. An apparatusaccording to claim 5, characterised in that each light guide (11)comprises a glass rod that has, along its longitudinal axis, dispersionmeans for causing the light to leave the glass rod along itslongitudinal axis.
 8. A method for automatic inspection of flatlypositioned pieces of cloth with a view to detecting impurities or otherirregularities; wherein the pieces of cloth are transported past acamera (10) that is, in cooperation with a digital storage unit,configured for producing a digital image of each piece of cloth orportions of each piece of cloth; and wherein the apparatus comprises oneor more light emitters (11) with a view to illuminating at least thatpart of a piece of cloth that is within the field of vision of thecamera (10), characterised in that each piece of cloth is transferredfrom a receiver conveyor (12) to a delivery conveyor (13), the field ofvision of the camera (10) being configured for comprising at least anopen area (14) between these two conveyors (12, 13), whereby the digitalimage is recorded during the passage of a piece of cloth from thereceiver conveyor (12) to the delivery conveyor (13).
 9. An apparatusaccording to claim 8, characterised in that—in the open area (14)between the two conveyors (12, 13)—a transparent cover (15) is arrangedbetween the piece of cloth and the camera (10).
 10. A method accordingto claim 8, characterised in that the receiver conveyor (12) and thedelivery conveyor (13) convey the piece of cloth past the transparentcover (15) in sliding abutment on the cover (15).
 11. An apparatusaccording to claim 10, characterised in that the transparent cover (15)forms a window in a closed container (16) in which the camera (10) islocated.
 12. An apparatus according to claims 8-11, characterised inthat the container (16) is located underneath the two conveyors (12,13).
 13. An apparatus according to claims 8, characterised in that thereceiver conveyor (12) receives pieces of cloth from a rotary ironer(1); and that the delivery conveyor (13) delivers the pieces of cloth toa folder machine (2) that have two or more destination options for afolded piece of cloth, wherein the relevant destination is determined byanalysis of the digital image of the piece of cloth.